Patent GB-582161-A (GB)
Title: Improvements in or relating to electrical apparatus for determining distances or short intervals of time
IPC: G01S1/02
Filed: 1940-02-21
Abstract: 582,161. Radiolocation; photoelectric apparatus. LAWSON, D. I., WEIGHTON, D., and PYE, Ltd. Feb. 21, 1940, No. 3289. [Classes 40 (iii) and 40 (v)] [Also in Group XXXVI (Appx.)] Apparatus for determining distances or short intervals of time comprises a cathode ray oscillograph, means for producing and applying one or more marker pulses and calibrated means for adjusting the position of the marker pulses on the screen of the oscillograph. In the apparatus shown in Fig. 1 for locating objects such as aircraft by transmitting radio frequency pulses of short duration and receiving the waves reflected from the object, the transmitter pulse is integrated in the saw-tooth generator 1 and is applied to one pair of plates of an oscillograph tube 2. A waveform may also be applied to the other pair of plates to allow the tube to be run at higher intensities without damaging the screen. In front of the oscillograph tube is a mask 3 containing two vertically arranged slits 4, 5 movable horizontally. Right-angle prisms or mirrors 7a, 7b, 8a, 8b, reflect, the light passing through the slits on to a photo-electric cell 6, the output of which is connected through an amplifier 9 to the vertical pair of plates of the receiving cathode-ray oscillograph 10 in opposite phase to the received pulses. The distance between the slits 4, 5 may be varied by micrometer screws 12, 13 so as to cause a corresponding displacement of the marker pulses 11a, 11b, on the oscillograph screen. The distance between any two received pulses on the oscillograph 10 may be measured by adjusting the two marker pulses to be in line with the received pulses and reading the distance on the micrometer scale. In the arrangement shown in Fig. 2 the cathode ray tube 2 for deriving the marker pulses is dispensed with, a pulse whose phase may be varied with respect to a given pulse being obtained from a controlling circuit. The grid 15 of a valve 14 is maintained at a high negative potential through a resistor 22. A condenser c is shunted across the output circuit and a resistor R is connected in the anode supply lead. The anode 16 is also connected to the anode of a diode 17, the cathode of which is connected through a resistor 18 to a variable tapping on a potential divider 19 connected across the H.T. supply leads. A further condenser 20 may be connected between the variable tapping and earth. The diode cathode is also connected through a condenser 21 to an amplifier and differentiating circuit. When a positive pulse is applied to the grid 15 the valve 14 conducts and discharges the condenser C. This then charges at a rate dependent on the time constant of the charge circuit to the potential of the tapping point on the potential divider 19. When the condenser is charged to this potential current passes through the diode 17 and a potential is produced across the resistor 18 and is fed to a differentiating circuit so as to produce a pulse at the instant when the diode commences to conduct. This pulse is indicated on the oscillograph screen together with the received pulse, with which it is made to coincide by adjusting either the charging capacitance or resistance or the position of the tapping point on the potential divider 19. The adjusting member, which may be operated by a micrometer screw, may be calibrated in microseconds, miles, &c.